Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.3.9 (glucose-6-phosphatase)
 3,081 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The subcellular localization of cathepsin B activity (EC 3.4.22.1) in three murine melanomas of increasing metastatic potential (Cloudman less than B16-F1 less than B16 amelanotic) was determined. Cathepsin B activity was localized in the heavy mitochondrial fraction of normal murine liver but in the light mitochondrial fraction of the metastatic melanomas; the localization of three other lysosomal hydrolases did not shift. Further purification of the light mitochondrial fraction into L-1 (density = 1.045 g/ml) and L-2 (density = 1.07 g/ml) fractions was achieved on a 30% iso-osmotic Percoll gradient. The L-1 fraction of liver and melanomas contained Na+, K+-ATPase activity; the L-2 fraction of liver contained four lysosomal hydrolase (cathepsins B and H, N-acetyl-beta-glucosaminidase, and beta-glucuronidase) and glucose-6-phosphatase activities. Ultrastructural examination revealed that the L-1 fraction consisted of membrane vesicles and the L-2 fraction of secondary lysosomes. In the B16 melanomas cathepsin B and N-acetyl-beta-glucosaminidase activities were found in both L-1 and L-2 fractions. Specific activities of the two enzymes in the plasma membrane (L-1) fractions increased in correspondence with metastatic potential. Cathepsin H and beta-glucuronidase activities were not localized in the plasma membrane fractions of the B16 melanomas. Localization of hydrolytic enzymes in the plasma membrane of metastatic tumor cells could result in focal dissolution of the extracellular matrix and thereby invasion and metastasis.
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PMID:Cathepsin B: association with plasma membrane in metastatic tumors. 345 10

Proximal tubules were isolated in highly pure form from rabbit cortices by a mechanical procedure that is known to preserve the structural and metabolic aspects of the tubular cells. Postnuclear supernates prepared from the isolated tubules were subjects to isopycnic centrifugation in linear sucrose gradients. The enzyme activities associated with the plasma membrane (gamma-glutamyl transpeptidase, amino-peptidase M, alkaline phosphatase, Na-K-ATPase, and phosphodiesterase I) exhibited sharp unimodal frequency-density profiles with a median density near 1.16 g/ml, which shifted to a heavier density when treated with digitonin. The lysosomal enzymes, N-acetyl-beta-glucosaminidase, alpha-mannosidase, and cathepsin B, and the peroxisomal enzyme catalase exhibited particle-associated activity near a density of 1.22 g/ml. Disruption of these particles by freezing and thawing resulted in these activities appearing in the rho = 1.10 g/ml region of the gradient where the soluble cytosolic enzyme, phosphoglucomutase, exhibited activity. Cytochrome oxidase activity typical of mitochondria gave a sharp unimodal profile at rho = 1.18 g/ml. Microsomal glucose-6-phosphatase and NADPH: cytochrome c reductase activities gave median densities near 1.16 g/ml, which did not change after incubation with digitonin. Galactosyl transferase activity gave a skewed profile at rho = 1.16 g/ml and showed a slight shift to heavier density after digitonin. This study of the enzymatic activities and density gradient distribution of the components of the proximal tubule cells provides the methodology for the further study of the cellular processing of endogenous and exogenous substances by this vital cell type.
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PMID:Analytical cell fractionation of isolated rabbit renal proximal tubules. 730 Jan 16